Ephrin-B2 is a candidate ligand for the Eph receptor, EphB6

No ligand has hitherto been designated for the Eph receptor tyrosine kinase family member, EphB6. Here, expression of an EphB6 ligand in the pro-B leu kemic cell line, Reh, is demonstrated by binding of soluble EphB6-Fc fusion protein to the Reh cells. The ligand belongs to the subgroup of membrane s panning ligands, as suggested by the fact that phosphatidylinositol-specifi c phospholipase C treatment did not abrogate binding of EphB6-Fc. Two trans membrane Eph receptor ligands, ephrin-B2 and ephrin-B2, were identified in Reh cells. Analysis of EphB6-Fc fusion protein binding to ephrin-B1 or ephr in-B2 transfected COS cells revealed a high-affinity saturable binding betw een EphB6-Fc and ephrin-B2, but not with ephrin-B1. In mice, EphB6 has prev iously been shown to be expressed in thymus. Here, we show expression of Ep hB6 in human thymus, as well as the expression of ephrin-B2 in both human a nd mouse thymus. We conclude that ephrin-B2 may be a physiological ligand f or the EphB6 receptor. (C) 2000 Federation of European Biochemical Societie s.